1. Field of the Invention
The present invention relates to a chemical toner composition and a method for preparing the same and, more particularly, to a chemical toner composition suitable for improving moisture resistance and controlling efficiently toner size, and a method for preparing the same.
2. Description of Related Art
Over the past years, the toner industry generally has used a pulverizing method to prepare toner, and the pulverized toner has characteristics of larger size, wider distribution range of particle size and various shapes. In the pulverizing method, the generation of dust, small molecular compounds and noise will badly influence environment, and for industrial security, there is a danger of dust explosions. Thereby, the pulverizing method needs further improvement.
Currently, in order to obviate the aforementioned problems, the toner industry utilizes chemical synthesis methods to prepare toner. The chemical synthesis methods are performed in a liquid phase, in which toner with a lower melting point can be obtained and thus the resultant toner is suitable for low-temperature fixing to meet the requirements of energy conservation and environmental protection. In the chemical synthesis methods, the size of resultant toner can be controlled by adjusting the amount of surfactants, stirring speed, polymerization time and the concentration of solution to achieve the characteristics of uniform components, bright color and high transparency. Accordingly, the chemical toner can has perfect particle shape, smaller particle size, narrower particle size distribution and improved flowability so as to meet the requirements of the modern printing technology, such as high speed, high resolution and full colour.
In comparison to the conventional pulverizing method, the chemical synthesis methods need briefer process and can reduce cost and consumed energy. Particularly, in the chemical synthesis methods, the generation of carbon dioxide, nitrides and sulfides can be reduced by about 40% to reduce the damage to environment. In addition, the chemical synthesis methods can more precisely control the size distribution to achieve a narrower range of size distribution. For example, fine toner with an average size of 7±2 μm can be obtained by chemical synthesis methods. More importantly, when the chemical toner prepared by chemical synthesis methods is used for low-temperature imaging, the efficiency for heat fixing can be significantly enhanced, the consumed power can be reduced and printers of smaller volume can be designed.
According to the process, the chemical synthesis methods can be mainly classified into: emulsion polymerization, encapsulation, solvent-mediated grinding and suspension polymerization. Although encapsulation and suspension polymerization have the advantages of brief process and no dust danger, several drawbacks, such as high cost, the limited shape of imaging particles to a sphere and the shape and the difficulty in controlling size of particles, exist in encapsulation and suspension polymerization. Particularly, encapsulation have another disadvantage of using organic solvents, while suspension polymerization causes environmental pollution due to the generation of a large amount of wastewater. Emulsion polymerization uses chemical coagulants to control the properties of particles, and has several advantages, such as low cost, brief process, the facility in controlling the shape of particles, solvent-free system, no dust danger and small amount of wastewater generated. Thereby, emulsion polymerization can meet the requirements of environmental protection and high equality and is the most popular method among all methods for preparing chemical toner. However, even if emulsion polymerization is predominant, there are several issues that remain unresolved, such as moisture resistance and toner adhesion.
Published U.S. Pat. No. 5,247,034 teaches that use of ammonium lauryl sarcosinate as emulsions or dispersants can improve moisture resistance and charge stability in comparison to general ionic emulsions. However, a drawback of poor toner adhesion exists in the use of ammonium lauryl sarcosinate as emulsions or dispersants.
European Patent No. 0660950B1 discloses that use of water soluble amines, including ethylene diamine, diethylene triamine, triethylene tetraamine, tetraethylene pentaamine and isophorone diamine, as coagulants can efficiently control aggregation speed. However, the excellent water solubility causes moisture absorption.
Published U.S. Pat. Nos. 6,673,500 and 6352810 teach that use of organic aliphatic amino esters, including diethylenetriamine, 4-aminobutyl ester, tertiary aminoester, aminosulfonate and aminosulfonite, as coagulants also causes moisture absorption due to their excellent water solubility.
Published U.S. Pat. No. 6,576,389 discloses that polyaluminum chloride (PAC) can be coated on silica to function as a coagulant. However, when polyaluminum chloride is used as a coagulant, rapid aggregation will cause the difficulty in controlling the size distribution. Although the amount of small particles can be reduced by using a large amount of polyaluminum chloride, re-aggregation will cause the formation of large particles. On the contrary, the reduction in the amount of polyaluminum chloride can efficiently control the average size in a desirable range, but the amount of small particles will increase.